He ______ sleep,although he tried to. One cup of coffee in the late afternoon caused him tostay awake almost all night.
句意：尽管他在尽力睡觉，但他无法入睡。下午晚些时候一杯咖啡使他几乎整夜保持清醒。
考查情态动词。wouldn't 将不；shouldn't 不应该；couldn't 不能；mustn't 不准，禁止。根据although he tried to可知他在尽力睡觉，此处应是转折，即“他还是不能入睡（睡不着）”。又根据tried可知是一般过去时，即couldn't。故选C。
He ______ sleep,although he tried to. One cup of coffee in the late afternoon caused him tostay awake almost all night.
—What a lovely present!Who sent it? __________it be your brother?
—It __________be my brother. He doesn't know today is my birthday.
—Excuse me, are the glasses Mike’s?
—No, they __________be Mike’s. He doesn’t wear glasses.
— Is that man your friend Tom?
—That man ________ be him,because he has gone to Canada.
—Sam, ________ I join you in the community service?
—Of course you can.
________you smell something burning? Go and see what's happening.
下面四个交通标志图是轴对称图形的是（ ）
—Could you hang out with me, Kate?
—Sorry, I ________. I have to do my homework.
“天问一号”在经历了7个月的“奔火”之旅和3个月的“环火”探测，完成了长达5亿千米的行程，登陆器“祝融”号火星车于2021年5月15日7时18分从火星发来“短信”，标志着我国首次火星登陆任务圆满成功，请将5亿这个数用科学记数法表示为（ ）
